Internal-combustion engine



June 17, 1930.

E. R. BURTNETT 1,764,147

I INTERNAL COMBUSTION ENGINE Filed April 11, 1929 4 Sheets-Sheet l INVENTOR June 17, 1930. E. R. BURTNETT 1,764,147

INTERNAL COMBUSTION ENGINE Filed April 11, 1929 4 Sheets-Sheet 2 I, r g r 711/ //IIIIIIIIIIIIIIIIII June 17, 1930. I E, R, BURTNETT 1,764,147

INTERNAL COMBUSTION ENGINE Filed April 11, 1929 4 Sheets-Sheet 3 June 17, 1930. E. R. BURTNETT INTERNAL COMBUSTION ENGINE 4 Sheets-Sheet 4 Filed April 11, 1929 8 q. MM mu m W K M MR. R m mg Y v M B & kk & w m my NQV mm mw. v W. n L i. la n W Ll. 7 NM ,QJIN. MW Wm q QW AW \muz I WW mm w Q R' w 5% M. Mm A L "2 g a Patented June 17, 1930 nvnnn'rr R. nunrnurr, or sun nose, 'camroamn mrnnnan-comausrroit ENGINE Application filed April 11,

My invention relates to an internal combustion engine of the two stroke cycle principle,

and more particularly to a balanced horizontal opposed cylinder unit and has for its principal objects the provision of an en-' gine having a balanced system of moving parts forming the embodiment of a system of working parts with four combustion units arranged so as 'to develop two uniformly spaced power impulses by each revolution of the crank shaft, to produce each of the two power impulses, coincident with a given revolution of the crank shaft by given events taking place synchronously within pairs of the four combustion units, which are respective 1y oppositely disposed with respect to the axis of the crank shaft, and of the same transverse plane therewith to effect balanced torque forces, in an opposite direction, in the respective transverse planes of the respective transversely opposed combustion units to effeet the transmission of the wer from pairs of synchronously actuate and oppositely moving pistons to the crank shaft in a manner developing a balanced application of the torque forces to the crank shaft, without producing any radial thrust with respect to the free rotation axially by the shaft, by providing the engagement of the said istons with crank pins'of the crank shaft t at are diametrically oppositely disposed with the axis of the crank shaft and relatively located in a given transverse plane-therewith.

Further objects of my invention are to provide an improved low cost, economical engine for light vehicle operation which will be of low gravity, inherently balanced, inherently' easily cooled, embodying parts, which are as a whole, easily manufactured and inherently of a design easilyand cheaply assembled, being valveless thereby eliminating valve grinding adjusting and attention, long lived, rugged, sim le, fool proof and silent of operation capa le of providing greater power from a given weight, cost of manufacture and operation with silence and perfect balance, which of a balanced unit lends itself to being produced and combined in multiplicities toward making up prime mover units of great power. Y

1929. Serial No. 854,266.

Further objects of my invention are to rovide a comparatively-simple, low gravity alanced engine unit? of low frontal area and made'up of a system of moving parts, which are, by the specific combination and arrangement inherently in dynamic balance when'in motion.

Further objects of my invention are to provide a valveless sin le crankshaft en ine of opposed multicylinger construction w ich is particularly adapted to be operated of the two stroke cycle principle with either asoline or Diesel, carburization or injection uel systems, specifically of a system of reciprocal and rotary parts so combined and arranged, that when in motion, all forces, inertia, centrifugal and torque, cancel out, without couple in close planes of opposed forces, making the use of counter balance weights unnecessary.

Further objects of my invention are to providean eight cylinder two stroke cycle internal combustion engine balanced unit, having horizontally opposed cylinders and a low cost single plane crank pin crank shaft of a general design particularly adapted for aeronautical and automotive purposes and for other prime mover purposes whereof the essential requisite is dynamic balance of the systeinof moving parts and whereof great power from a givenweight and engine cost is required.

By my improved construction, I have provided an engine in which the inertia forces,"

the centrifugal forces and the torque forces will develop in a manner. of. respective planes which the respective forces, themselves of a kind, will be self counter balancing'within approximately singular planes and in which all the forces at all times are transmitted to the crank shaft entirely along its axis, longitudinally with respect to the engine structherefore permit the crank shaft crank pins and main bearing sections being constructed of comparatively small diameters, facilitating great speed and acceleration without excessive centrifugal bearing loads.

The foregoing features of balance are of very great importance in the present day and as the demand increases for engines of greater power from a given weight, capable of operating continuously at greater speed,'of-

a lesser number of parts, of less production and operating cost the foregoing features as disclosed as being the result of my present invention, will be found paramount and es sential in the art of producing internal com- ,spectively adapted to admission'of the scavenging charge; I l v Fig. 3 is a vertical longitud nal section taken on line 3-3 of Fig. 1; Fig. 4. is a vertical longitudinal section taken on line 44: of Fig. 1;

Fig. 5 is a horizontal diagrammatic, view of the-pistons and crank shaft illustrating the directionof inertia forces with arrows located respectively in the various inertia force planes, by weights indicated by #2 representing to exist, when the bodies are in I motion, in the respective piston stroke planes;

Fig. 6 is a horizontal diagrammatic view of the same'for'm as Fig.- 5 with theexception that the respective pistons are shown to be in the positions at the end of opposite stroke movements comparatii'ely with the piston posit-ions as illustrated in Fig. 5;

Fig. 7 is a diagrammatic View of the-cranks of the crank shaft illustrating the relative positions of the respective cranks of the shaft;

Fig. 8 is ahorizontal diagrammatic view showing the two pairs of pistons respectively in pairs of cylinders relatively located on opposite sides and at opposite ends of the crank shaft and associated respectively with the four cranks of the eight crank pin crank shaft which are co-axi'al and representing a longitudinally balanced half of the crank shaft Fig. 9 is a horizontal diagrammatic view, similar to Fig. 8 and showing the other two pairs of pistons respectively in pairs of the other four of the eight cylinders which are respectively relatively located on opposite sides and at opposite ends of the cran shaft and associated respectively with the other four of the eight crankpins of the shaft may be taken as the which are co-axial and represent longitudinally the other balanced half of the crank shaft;

In Figures 5, 6,8 and 9 the lines EE indicate the rocking axis of the moving bodies of the engine longitudinally with respect to the rotary axis of the structure.

In Figures 5, 6, 8 and 9 the lines FF indicate the rotary axis of the structure and longitudinal plane'of the engine also.

Referring by numerals to the accompanying drawings which illustrate a practical embodiment of my invention, 10 designates a crank case within which a crank shaft 11 is rotatably journaled within three main bearings 12, 13 and 14. i

.This crank-shaft is provided with eight cranks, the crank pins of which are designated by the numerals 15,16, 17, 18, 19, 20, 21'and 22 respectively. Pins 15, 17, 20' and 22am arranged co-axial and form onehalf of-the balanced shaft while pins 16, 18, 19 and 21 are arranged co-axial and form the other half of the balanced shaft. .The four respectively co-a-Xial pins 15, 17, 20 and 22 are relatively disposed diametrically opposite or 180 apart with the other four respectively co-axial pins 16, 18, 19 and 21 with respect to the axis of the crank shaft. Upon examination it will be seenthat each co-axial group of four crank pins respectively occupy balanced positions longitudinally from the center of the crank shaft, thus, when the shaft is in motion the entire rotary mass will be in dynamic balance. The eight crank pins are formed in one plane which diametrically intersects the axis of the crank shaft andpermits the eight pin shaft to be easily forged and cheaply and efliciently machined.

Fixedto'and extending from the crank case 10 on two opposed sides in'a horizontal plane therewith are two rows of cylinders, the two rows of cylinders are illustrated to be respectively formed as ntegral constructions designated respectively by the numerals 31 and 32. Four cylinders are provided in each' of the two rows, the four cylinders of the two rows embody anv eight cylinder combination with the respective cylinders designated bythe numerals 23, 24'," 25. 26, 27, 28 29 and 30;

A cylinder headgmember 33. is provided preferablydetachable with the outer ends of each of the two rowsof four cylinders. Two compression clearance chambers are provided in each cylinder head member and respective- 1y designated in each instance by the numeral 34, each compression clearance chamber provides a passage communication between the piston stroke sweep chambers of two parallel and adjacent cylinders and respectively form thereby dual cylinder combustion chambers of each adjacent parallel pair of cylinders arranged in a given one of the two rows.

Exhaust ports 35 are formed intermediate the-ends of one cylinder of each' dual c lindereach row to facilitate the provision of a direct outlet of comparatively large area and the inlet ports are preferably located in the Genter cylinders of each row to facilitate the provision of a Siamese inlet chamber41 having a single supply duct communicating with the inlet ports of the two inlet port cy inders of each row of cylinders.

Eight pistons are rovided, one'piston ar-v ranged reciprocal wlthin' each of the eight' cylinders. The eight pistons are respective-' ly designated in simultaneous reciprocal pairs respectively arranged in a given row of cylinders in the manner as follows: A.A of one dual cylinder chamber, B -B of a second dual cylinder chamber, CC of a third dual cylinder chamber and D 2 of the fourth dual cylinder chamber, the A and B pistons being arranged on one side of the crank shaft and the C and D pistons 'bein arranged on the opposits side of the cran shaft.

Eight connecting rods are provided, one rod connecting one of the eight pistons respectively with one of the eight crank pins of the crank shaft, the rods are designated by the numeral 39.

An ignition device 40 is provided with each:

clearance chamber of each dual cylinder chamber.

An inlet passage duct 43 is formed in. each cylinder block and similar inlet passage ducts 49 and 50 are form-ed in the two sides of the upper'part of the crank case. The passage ducts 49 and 50 of the crank case communicate respectively on each side with the passage duct 43 of the coinciding cylinder block, the duct 43 of each cylinder block is formed to communicate with the inlet passage chamber41 in communication with the inlet ports of both inlet port cylinders of the respective cylinder block and the ducts 49 and 50 of the crank case terminate at a common port 48 to which a compressor illustrated and designated by the numeral 52 having a discharge port 54 may be attached.

An inlet port to the compressor chamber is designated by the numeral 53, a carburetor 55, for illustration, may be connected with the compressor by means of an elbow fitting 56. A driving gear between the compressor parts and the crank shaft of the engihe is designated by the numeral 60.

On the upper and lower sides of each cylinder block the inlet passage chamber 41 is preferably open for its entire length through the side walls of the respective blocks facilitating examinating and cleaning of the ports of the centrally located cylinders, these passages'41 are closed on the upper side by plates The exhaust ports are preferably located in the end cylinders of beneath the drop between t 'case to which an oil plates 51, the on their inner sides with a drain groove 57 which preferably inverts to the center, which point is directly oint where the inlet supply duct 43 of each b ock communicates withthe passage chamber 41 and directly between the two central cylinders which are spaced apart sufiiciently to ermit the liquid particles, usually termed as eav' ends of the fuel mixture, to

ly into the drain 57, facilitatln the flow of only the dry well vaporized uel mixture reaching the inlet ports of the adjacent cyl-.

inders.

Drain pipes 46 are provided respectively in communication with the drain 57 of each under plate 51 of each block and join with a main drain pipe 47 which extends to a point communicating with the induction side of the compressor whereof the vacuum will effect the withdrawal of the undesired fluid residual from the inlet passages of each cylinder block preventing pooling of the fuel liquid and uneven operation of the engine under variable conditions.

The crank case mabe made barrel type with center and en main bearings con.- structed removable within retainer bushings if desired and the rods may be assembled with the crank shaft by admission of the operator through the lower side of the crank pan 61 of ample size may be secured.

A fluid outlet 44 is preferably located directly over each cylinder at a point near the crankwardly extending base of each com-- mon cooling fluid cell of the respective cylinder block and a fluid inlet port 45 is preferably located on the underside directly under the ignition device at the headward end of each cylinder. The location of the cooling fluid inlet and outlet ports with respect to each combustion unit isdetailed to assume improved cooling of the cylinder head walls and particularly the parts immediately surrounding the ignition device, the admission of the cooling fluid at first to the head end of the cylinders and on the under side thereof assuring the fluid first engaging the area of the combustion chamber walls, which is subjected to the highest temperature, and also the circulation of the water from the under side upward around e respective c linders directthe combustion cylinders,

horizontal arrangement of cylinders and which the opposed ducts constructed in the crank case provides without greatly increasing the height of the compressor relatively with respect to the axis of the crank shaft and the mean center of gravity of the engine structure.

The operation of myimproved' engine is accomplished in the conventional two stroke cycle scavenging manner, a compressor being depended upon for forced induction of scav.-"

enging air or gaseous mixture, as the case may be, the pistons within the respective dual parallel cylinder combustion chambers being adapted to control the admission and exhaust ports respectively of the two cylinders'of each chamber.

Obviously the development of dual synchronously timed power impulses in opposed units is accomplished by the specific arrangement of the pins of the shaft and therelative association of the opposed pistons with the respective pins. It will be seen that in my improved construction, the opposed pistons of a given pair of commonly connected opposed cylinders, occupying a given transverse plane with the crank shaft at one end of the structure, are connected to the respec-' tive end crank pins which are on dead centers on the near side to the respective cylinders of which the respective pistons therein are connected and that the opposed pistons of the other pair of commonly connected opposed cylinders respectively occupying another given'transverse plane with the crank shaft, at the other end of the structure, are

connected to the respective end crank pins,.

of the other end, of the shaft, which are relatively rotatively of positions on dead centers furthermost from the respective cylinders ofwhich the respective pistons therein are connected.

Obviously this combination and relationship of reciprocatory and rotary parts providestwo dual synchronously timed op posed power impulses to the crank shaft by each revolution of the shaft, the two opposed power impulses being relatively developed 180, apart with respect to the rotation of the crank shaft and the combination and arrangement of parts, forming the embodiment of my improved engine, further accomplishes the development of only-opposed forces of any nature, in a given plane of respective forces and completely throughout the entire system of moving bodies, leaving the crank shaft freely rotatable in the main bearings with only theushaft weight friction as a mechanical consideration between the crank shaft and the journal bearings thereto.

In my improved construction each power impulse is transmitted to the crank shaft through four-big end bearin s of four rods to four respectively separated crank pins of exactly opposed weightand synchronously transmitting the same force of exactly opposed angularity of thrust, obviously there for, the torque is produced rotatably of the crank shaft from four pistons simultaneous-. ly and directly to four points of the shaft and distributed over exactly one half of the crank shaft. This latter feature being of great importance to mechanical perfection in an engine, almost equally so, for either extremes of the field, namely small high speed supercharged or nonsupercharged engines or very large industrial units whereof the unit forces are tremendous.

- With reference to the 9, of the accompanying drawings, a study of the Figures 5 and 6 will illustrate the per fect balance of the inertia forces in any position, in Figure 5 it will be seen that pistons A and A representing the synchronously actuated reciprocatory members of a given end pair of cylinders of the first side are at head end center and their respective inertia forces are represented as being re spectively of 2# outward from the axis of the crank shaft in the stroke plane of each respective piston, at the same moment pistons D and D of a pair of opposed cylinders of tho other side anddesignated as .the second side and located at the opposite end of the structure, are in the position of crank end center and their respective inerita forces'are represented as being also respectively of 2# outward from the axis of the crank shaft,-but. from the opposite side, therefore the inertia forces of pistons A and A and'relatively longitudinally stepped and opposed pistons D and D are of the same transverse direction collectively toward the s'aidfirst side and since the four respective endwise crank pins are co-axial and longitudinally balanced, the combined inertia forces of the four respective pistons, of offset opposed cylinders, of opposite ends of theopposed rows of cylinders, produce a uniform weight in a giv'en'direction and toward the said first side away from the axis of the crank shaft.

With further reference to Figure-5 it will be seen that pistons B and B of cylinders located at the other end of the said first side, are in the position of crank end dead center and their inertia forces are respectively represented as being 2# respectively Figuiesb, 6, 8 and in each stroke plane of the respective pistons and in the direction of the said second side andat the same moment the position of pistons C and C of the fourth air of cyhnders, respectively located on t e said second side and at the ofpposite end relatively with the c linders o the first side containing pistons 1 and B are of head end dead center, and being of c linders of the said second side, the inertia orces of the respective pistons are likewise represented as respectively of 2# and of an outward direction from the axis of the crank shaft toward the said second side.

It will be seen that the four pistons 13 and B and C and C are connected to four coaxial cranks which are of relatively longitudinally balanced positions and relatively diametrically opposite the other four co-a'xial cranks to which the pistons A A ,'D, and D are connected, therefore the inertia forces of pistons B B G and C are of the same transverse direction collectively toward the said second side and since the four respective endwise crank pins, to which the said pistons are connected, are co-axial and longitudinally balanced the combined inertia forces of the said four pistons B B", C and C produce a uniform weight in agiven direction along the axis of the shaft toward the said second side, thus the combined forces of the pistons A A D and D in an outwardly direction from the axis of the crank shaft toward the said first side are equal and perfectly cancel out, without the sli htest rocking couple, the combined inertia orces of the pistons B B 0 and C of which the forces are collectively produced in an outward .direction from the axis of the crank shaft toward the said second side.

Figure 6 illustrates the relative position and direction of inertia forces of the pistons when the pistons are respectively at opposlte end centers from that shown in Fi ure 3 and as caused-by one half revolution of the crank shaft from the shaft position as shown in Figure 5.

With reference to Figures 8 and 9 of the' accompanying drawings, Fi ure 8 illustrates the two pairs of ofi'set an oppositely disposed pistons and their connections with one co-axial group of four crank pins, the arrows indicating the direction of the inertia force of the respective pistons showing the forces to be collectively in common toward the said first side, Figure 9 illustrates the othertwo pairs of relatively oifset and oppositely disposed pistons and their connections with the other or second relatively co-axial group of four crank pins of the crank shaft, which second group of crank pins are relatively rotatively disposed 180 pins, the arrows indicating the direction of the inertia force of the respective pistons counter to the forces of the other four tatively of a crank pin position res apart with the said' first group of four relatively co-axial crank showing the forces to be collectively in com montoward the said second side, directly pistons as illustrated 'in Fi re 8. It is to be understood that a multiplicity of my improved balanced engine units respectivel of eight cylinders and eight crank pin cran shaft ma be constructe in one integral structure if desired and that the section of the crank shaft adapted to one eight cylanother section of crank shaft, respectively related to another unit of eight cylinders, 1+0- ctive y providing a differential of pin posltions rotatively with respect to the pin positions rotatively of another given section of shaft adapted to another given unit of cylinders to produce a greater frequency of power impulses by one revolution of the crank shaft.

It will be further understood that my invention as to itsbroader aspects is not limited to the precise construction herein set forth, as many changes may be made therein without departing from the spirit of my invention and without sacrificing its chief advantages.

I. claim as my invention:

1. In an internal combustion engi'ne,-two rows of four cylinders each arranged to form a horizontal opposed structure, the eight cylinders being arranged in four pairs with the head ends of the members of each pair connected by a common compression and combustion clearance chamber, one cylinder of each four pairs having exhaust ports and the other cylinder of each four pairs having inlet ports, eight pistons, one piston arranged for reclprocato movement within each of the eight cylin crs, a crank shaft having elght crank pins disposed in two co-axial groups of 'four crank pins each, the eight crank pins being formed in one plane, two pistons of each of the two opposed rows of cylmders being connected respectively of opposed rows of cylinders to two adjacent crank pins of one co-axial group and an ignition device provided with each common compression chamber.

2. In an engine, eight cylinders arranged in two rows of four cylinderseach, the chambers of the first and second cylinders from each end of each of the two rows being connected at their head ends by a common compression clearance chamber, pistons arranged for operation within all the cylinders, the two rows of cylinders bein parallel and axially dlsposed in a common parallel plane, a crank shaft having eight throws with crank pins thereof relatively disposed rotatively in two co-axial groups of four crank pins each, the "first and third crank pins from each end of the shaft being co-axial, the second and fourth crank pins from a d o t ha t being coaxia inder unit may be relatively disposed with arranged with axes the respective crank pins of the two co-axial groups being alternately disposed with re spect to their longitudinal order relatively diametrically opposite with respect to the axis of the crank shaft, the crank shaft being disposed between the two rows of cylinders, the pistons of the first and second cylinders respectively from a given end and relatively of opposite ends transversely of the two op;- posed rows of cylinders be ng connected respectively of palrs of ad acent commonly connected cylinders respectively to the first the crank shaft whic and second relatively units, comprising in combination four commonly connected pairs of relatively axially parallel cylinders, the four pairs of cylinders being arranged in two rows of two commonly connectedpairs of cylinders each, the cylinders of the two rows being relatively axiall disposed in a common .plane and space apart sufficiently to permit the installation of a crank shaft between the two rows of cylinders, a crank shaft having eight crank throws disposed between the said two rows of cylinders, the cylinders of the two rows being respectively disposed coincident in the planes of the eight crank thro'ws of the crank shaft and alternately of rows respectively coincident with every other crank throw thereof, the eight crank pins of the eight crank throws being disposed in two co-axial groups of four crank pins-each, the first and third crank pins res ectively from each end of the crank shaft eing co-axial and comprising one of the said two co-axial groups. of four crank pins, the second and fourth crank pins respectively from each end of the crank shaftbein relatively co-axial and comprising the ot erof the said two co-axial groups offour crank pins, the two coaxial groups of crank pins being relatively diametrically oppositely disposed 180 apart, eight pistons, one piston arranged reciprocal within each cylinder, the four pistons of each row of cylinders being connected in pairs respectively of commonly connected cylinders of each row with adjacent co-axial pairs of crank pins of both of the two diametrically oppositely groups of co-axial crank plns. I

4..In' an engine the combination of eight cylinders, eight pistons, a crank shaft having eight crank pinsand connections between the said eight pistons singularly with the eight crank pins thereof, the disposition of.

the eight cylinders in two rows each comprising four opposed cylinders to the other row,

the crank shaft being interposed between the two rows of c linders, all the cylinders being axially para'l el, the eight crank pins being relatively disposed in two group-s of four crank pins each, the four crank pins respectively of each of the two groups being relatively disposed axially in line and axially parallel with the axis of the crank shaft, the

two groups of axially aligned crank pins being'relatively -rotatively spiced 180 apart, .1

every other crank pin from a given end of the crank sha'ft being formed in a given one of the two axially aligned crank pin groups and the pistons of the first and second cylinders relatively of opposite ends of each of the two opposed rows being respectively connected to the respective endwise two of the four axially'aligned crank pins of a given axially aligned group of crank pins of the crank shaft. V

5. In an engine, eight cylinders, eight pistons, one piston arranged for reciprocatory movement within each of the eight cylinders, a crank shaft, eight crank throws formed of the crank shaft, a crank pin formed of each of the eight crank throws of the shaft, the eight crank pins being disposed in two coaxial planes of four co-axial crank pins each, the four crank pins disposed in one common axial plane being relatively"rotatively 'disposed 180 apart with the other four crank pins relatively disposed in the other of the two common axial planes, the four crank pins comprising either of the two co-axial groups respectively of a common axial plane being separatedvand spaced longitudinally and alternately by the respective pins of the other four relatively co-axial crank pins comprising the pther of the two co-axial groups of pins respectively of, another common axial plane, the pistons of the first and second cylinders of each ofthe two opposed rows and respectively diversely located at oppo-- site ends of the rows thereof being connected respectively in pairs of relatively adjacent cylinders ,to' the first and second relatively co-axially disposed crank pins of the shaft from the respective end of the shaft which is coincident with the respective cylinders.

6. In a two stroke cycle internal combustion engine, the combination with eight cyl- I and seventh crank pins from either end of the shaft being formed of a common axis, the first, third, sixth and eighth crank pins from either end of the shaft and of co-axial alignment being axially relatively rotatively disposed 180 apart with the axes of the said third, fourth, fifth and seventh crank pins from either end of the shaft and respectively being of co-axial alignment, eight pistons, one piston arranged for reciprocatorymovement in each of the said eight cylinders, the four pistons of the cylinders of one side of the said opposed cylinderformation being respectively connected with the first, third, fifth and seventh crank pins from a given end of the shaft and thefour pistons of the cylindersof the other side of the said opposed cylinder formation being respectively connected with the first, t.hird, fifth and seventh crank pins from the other end of the crank shaft.

connected to the first, third, fifth and seventh crank pinsfrom one end of the crank shaft,

the other four pistons respectively disposed on the other side of the crank shaft beingv 7. In an eight cylinder horizontal opposed internal combustion engine, thecombination of a balanced system of moving bodies comprising, a crankshafthavmg elght crank throws, a crank pin formed of each crank throw, the eight crank pins being arranged 1n two co-axial groups of four crank plns' each, each ad acent pair of crank pins belng relatively disposed'180 apart, every, other crank pin being axially disposed coincident with three other crank pins, eight pistons, four pistons disposed on one side of the crank shaft and arranged reciprocal respectively within cylinders comprising one of the two opposed groups, the four other pistons being disposed on the diametrically opposite side of the crank shaft and arranged reciprocal within other cylinders which comprise the other of the two opposed groups and the four pistons of either of the two opposed groups of cylinders being respectively separatel connected to every other one of the cran pins of the crank shaft.

8. The combination in a two stroke cycle internal combustion engine, of eight cylinders, eight pistons, one piston arranged'for reciprocatory movement within each of the eight c linders, a crank shaft having eight crank throws formed in a single-plane, a crank pin formed of each of the eight crank throws, the eight cylinders being arranged in two rows of four cylinders each on two rela- I tively diametrically opposite sides of the crank shaft, each row of cylinders being coincident with the axis of the crank shaft, the eightcylinders being disposed with axes parallel. the four cylinders of each side being formed in pairs, the chambers of the members of each pair being connected at their head ends by a common compression clearance chamber, the first, third, sixth and eighth crank pins from either end of the shaft being" co-axial, the second, fourth, fifth and seventh crank pins from either end of the crank shaft being co-axial, the said first, third, sixth and eighth crank pins being disposed relatively rotatively 180 apart with the said second, fourth, fifth and seventh crank pins, the four pistons on one side of the crank shaft being 

